Optimization of sugar recovery from pineapple leaves by acid-catalyzed liquid hot water pretreatment for bioethanol production

Abstract

Lignocellulosic residue has been demonstrated to be a carbon-neutral and sustainable resource that can provide a wide range of biobased fuels, chemicals and materials. In this study, central composite-based response surface methodology (RSM) was used to optimize process condition in acid-catalyzed pretreatment of pineapple leaves under the liquid hot water (LHW) technique. The experiment was conducted with consideration of the influencing parameters (type of acid catalyst, concentration, reaction temperature, and residence time). After pretreatment, the enzymatic hydrolysis of solid residue performance was evaluated to find the optimal pretreatment conditions based on the maximized glucose yield. The RSM method could estimate a maximum glucose yield of 91%, which could be obtained at a sulfuric acid concentration of 0.61 M and a temperature of 143.2 °C for 38.4 min. The results also showed valuable sugars with a low level of byproducts detected in the soluble phase during LHW pretreatment. Further study for bioethanol production found that the fermentation process gave the highest theoretical ethanol yield of 94.68% at 5% solid loading. However, a high solid loading (15%) could improve the performance in terms of productivity with 0.63 g/L-h. The pretreated pineapple leaves also involved the analysis of physiochemical characteristics. These properties clearly showed the destruction of hemicellulose and lignin, resulting in increased enzyme digestibility and further improvement of fermentability for ethanol production. The results of the present study showed that an acid-catalyzed LHW pretreatment could be effectively applied for the utilization of pineapple leaves in derived bioproduction.

Keywords

• Lignocellulose
• Pineapple leaves
• Acid-catalyzed liquid hot water pretreatment
• Enzymatic hydrolysis
• Derived sugars
• Ethanol production